Earthlings will witness Mercury make a rare passage between our planet and the Sun on Monday, appearing as a black dot tracking the surface of the star we share with the solar system’s smallest planet. Mercury completes an orbit every 88 days, and passes between the Earth and the Sun every 116 days, according to the Royal Astronomical Society (RAS).

But its orbit is tilted in relation to Earth’s, which means it usually appears — from our perspective — to pass above or below the Sun. Thirteen times each century, however, the two orbits align such that even amateur astronomers can see the tiny planet tens of millions of kilometres away. “It is always exciting to see rare astronomical phenomena such as this transit of Mercury,” RAS president Martin Barstow said in a statement. READ MORE